When Insulation Turns Black

Insulation Moulding

Any insulation that turns black and smells muggy has most likely become the victim of mould growth. Mould growth can be easily seen when glasswool insulation becomes discoloured and black patches present. Unfortunately, condensation near your insulation can be the reason for mould growth. Condensation formation can be hard to detect and its usually too late when insulation has mould growth on it. Mould growth may be caused by a number of factors including; lack of air flow in cavity spacings, water leakage and humid climate zones. Taking appropriate measures to reduce the risk of mould growth is worthwhile and could save you a lot of hassle in the long run.

Can black mould grow on insulation?

Yes, mould can grow on glasswool insulation in the same way it grows on any other surface, or material, where there’s a presence of water and mould spores. Both water and mould spores can find there way into your home and mould growth begins. There are also a number of environmental factors that contribute to the risk of mould growth, these include;

  • Large number of people living in the house
  • Using heating and cooling appliances excessively.
  • Climate zone of the building
  • Buildings that don’t get sun, or are excessively shaded

How do I know if I have mould in my insulation?

The fastest way to check if you have mould growth on your glasswool insulation batts is to inspect the insulation for any signs of black/dark discolouration. Another indicator of mould growth is the muggy smell that accompanies it, make sure you are aware of this smell as it can be a great indictor of mould growth when you are inspecting your ceiling or underfloor cavity areas. Ensure you also look out for water leaks or moist areas to try and resolve any condensation issues. Repair the source of moisture such as a leaking pipes or holes in the roof, to prevent mould growth from occurring again.

How do you remove black mould from insulation?

If you have mould growth on your glasswool insulation, we recommend removing all affected insulation and any insulation that is in close approximation to the mouldy material. Removing mouldy insulation requires protective gear such as; disposable overalls, gloves, goggles and a face respirator to prevent inhaling mould spores which can irritate your lungs. Remove both affected insulation and drywall and dispose of it immediately in appropriate waste removal containers. We recommend having a professional removalist to ensure all mouldy insulation is removed correctly.  Remember it is important to remove all affected material as mould can have adverse effects on your health such as inflamed airways and cause long term health problems such as asthma.

Replacing Mouldy Insulation with Glasswool

After all mouldy insulation has been removed, and moisture issues are fixed, we recommend re-installing new glasswool insulation. Earthwool insulation is easy to install as it is soft to touch and low itch. Installing insulation in your walls, ceiling and floor can reduce your energy bills by up to 45%. When choosing which insulation type is right for you, remember that the higher the R-value the greater the thermal performance.

2 thoughts on “When Insulation Turns Black

    • Pricewise Insulation says:

      Hi Barbara,

      Thanks for your comment!

      The presence of blackened insulation often indicates air leakage in and out of your home. The air carries particles, dust, and moisture which overtime build up in the insulation (which acts as a filter) and causes the insulation to blacken.

      Older homes often lack airtightness, particularly those without proper vapor barriers. It’s crucial to note that if the insulation is damp, it is advisable to consider removal. This precautionary measure is especially significant to prevent the potential formation of mould. Keeping your insulation dry and well-maintained is key to ensuring its optimal performance.

      Please don’t hesitate to call us on 1300 729 639 if you need further assistance. We’d be happy to help.


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